The present invention relates to a clamping element, in the form of an annular disk, for a pipe coupling between the ends of two butt-joined pipes. Each pipe carries a flange or the like loosely slipped onto its respective end. The flanges may be braced against one another, and each flange is provided with a clamp chamber into which a corresponding clamping element fits. The clamping element suppprts itself on the end of the pipe by means of an inner, radial clamping edge. A clamping surface of the clamp chamber overlaps the clamping element with respect to an outer, radial clamping edge. The clamping element has an axial configuration such that an axial compression force applied to the element results in an increase in its external diameter and a decrease in its internal diameter. A seal which surrounds the impact point of the joint is also provided.
A pipe coupling of the above generic type is disclosed in European Application No. 0 087 702. This pipe coupling may be mounted on smooth pipe ends that are merely deburred. Wrenches suitable for the screw joints are the only mounting tools required. The release of the pipe coupling is also very simple. This configuration has been proven in actual practice, especially in sealing against high pressure.
In the known coupling, each clamping element consists of at least one convex disk. The disk may be designed as a flat spring or a toothed, disk-shaped clamping element. The inner, radial clamping edge of each clamping element may be scarfed so as to form a light positive lock between the clamping element and the outer wall of the pipe, in addition to the frictional connection when the joint is tightened.
A comparable pipe coupling may be found in French Pat. No. 2 237 102. In this case, the clamping elements are in the form of relatively narrow clamping rings. The annular section of these rings is inclined at an angle of approximately 30.degree. to the plane of the clamping element. However, experiments have shown that clamping elements with an inclination of this magnitude pass from the elastic into the plastic range when the pipe coupling is tightened, so that proper functioning of the clamping elements is no longer assured after the installation. Furthermore, an inclination of this type requires very large forces to be applied by the screw joints. This necessitates the use of screw joints that are overdimensioned with respect to those used in fields of application of pipe couplings of this type.
Further problems arise in connection with the above-described pipe coupling when the pipes to be joined consist of a brittle material, for example, phenolcontaining resins with fillers. The inner clamping edge pressing into the surface of such pipe occasionally causes the body of the pipe to crack.